Turbomachines include a rotational shaft known as a rotor and a stationary portion known as a stator where a gas tight seal is required between the rotor and the stator. Turbomachines include, but are not limited to steam turbines, gas turbines, electric generators, compressors, and pumps. For example, an electric generator typically includes main components like a rotor and stationary electrical conductors. The rotor typically includes rotor electrical conductors that produce a magnetic field when energized with an electric current. If the energizing current is direct, then the magnetic field produced is constant in magnitude. However, as the rotor rotates, the field strength at a stationary point will vary as the magnetic field poles pass by. The stationary electrical windings surround the rotor and are arranged to intersect the rotating magnetic field such that an alternating current is induced in the stationary electrical windings. The stationary windings are connected to an electrical network such that the induced alternating current is distributed to many users.
Operation of the generator produces heat within the internal components of the generator. Typically, generators are cooled by a cooling medium, such as air, water or hydrogen gas. In the case of hydrogen gas, care must be taken to prevent mixing of the hydrogen gas with the surrounding air to avoid an explosive mixture of hydrogen and oxygen. Typically, hydrogen cooled generators are operated under positive pressure and high hydrogen purity to ensure that a combustible mixture of hydrogen and oxygen does not result within the generator. A hydrogen cooled generator is typically enclosed within a strong shell like frame that can not only support the weight, operational and transient loads of the generator, but also contain the hydrogen gas and prevent it from escaping into the atmosphere where it can form into a combustible mixture.
There are many locations on the generator where internal components of the generator must penetrate or pass through the frame, such as the rotor and the stationary electrical conductors. Because the rotor must be free to rotate, a sufficient clearance must be provided between the generator frame and an outer surface of the rotor. Typically, a gland seal is provided between the rotor and the frame to prevent the rapid escape of hydrogen gas.
A gland seal, also known as a hydrogen seal, is well known and functions by forcing a fluid, typically sealing oil, under a pressure greater than that exerted by the opposing hydrogen pressure through a radial gap provided between the rotor and a sealing surface of the gland seal. The sealing oil effectively seals the gap between the rotor and the gland seal thus preventing the leakage of the hydrogen gas and the resultant dangerous mixture of hydrogen and air.
To effectively seal the generator, the radial gap between the gland seal and the rotor must be as small as practical while leaving sufficient clearance for rotation of the rotor. The diametrical clearance between the gland seal ring and the rotor is proportional to the rotor diameter at the axial location of the gland seal ring and typically is on the order of several thousands of an inch as measured on diameter. Due to the tight radial clearance between the rotor and the gland seal, radial and angular alignment of the gland seal to the rotor is critical. Improper alignment of the gland seal can lead to contact of the rotor with the gland seal causing impermissible wear of the gland seal and/or excessive rotor vibration. Both situations are unacceptable and will likely result in a forced shut down of the generator to remedy the situation.
The rotor is typically supported at its opposite ends by bearings arranged outside of the gland seals, see FIG. 1. Due to the large span between the bearings and the weight of the rotor, the rotor will, sag in its middle causing a difference between a theoretical centerline of the machine and an instantaneous centerline of the rotor, see FIG. 5. The rotor sag forms an angle between the instantaneous rotor centerline and the theoretical centerline of the machine. If the gland seal is aligned to the theoretical machine centerline, the slope of the rotor at the axial location of the gland seal will result in an inconsistent radial gap from an outboard edge of the gland seal to an inboard edge of the gland seal and from a top to a bottom of the gland seal resulting in uneven pressure and flow of the sealing oil circumferentially around the gland seal. Therefore, the gland seal should advantageously be aligned to the instantaneous angle of the rotor and not to the theoretical rotational centerline.
The orientation of the gland seal is determined by the gland seal housing that supports the gland seal. Furthermore, the orientation of the gland seal housing depends upon an orientation of a mating surface between the gland seal housing and a structural bearing support bracket that the gland seal bracket attaches to.